Control mechanism for hydraulic apparatus



26, 1952 v. v. BLASUTTA EIAL 2,608,182

CONTROL MECHANISM FOR HYDRAULIC APPARATUS Filed A aril 15, 1948 5 he t -Sheet 1 '67 I 'fiillll lllll Lil INVENTOR.

, VICTOR V. BLASUTTA -WENDELL E. RENICK BY zM/AMMW Aug. 26, .1952 v. v. BLASUTTA ETAL 2,608,182

CONTROL MECHANISM FOR HYDRAULIC APPARATUS Filed April 15, 1948 5 Sheets-Sheet 2 FIG. lC.

FIG. l5.

7 FIG. /A.

IN VEN TOR5 VICTOR V. BLASUTTA WENDEL E. RENICK Aug. 26, 1952 v. v. BLASUTTA ETAL 2,608,182

CONTROL MECHANISM FOR HYDRAULIC APPARATUS Filed April 15, 1948 5 Sheets-Sheet a VICTOR V. BLASUTTA WENDELL E. RENICK Aug. 26, 1952 v. v. BLASUTTA EI'AL 2,608,132

CONTROL MECHANISM FOR HYDRAULIC APPARATUS 5 Sheets-Sheet 4 Filed April 15, 1948 INVENTOR.

FIG.. 3

VICTOR V. BLASUTTA WENDELL E. RENICK 26, 2 v. BLASUTTA ETAL 2,608,182

CONTROL MECHANISM FOR HYDRAULIC APPARATUS Filed April 15, 1948 5 Sheets-sheaf: 5

' IN VEN TOR.

VICTOR v. BLASUTTA WENDELL E. RENIGK Patented Aug. 26, 1952 GONTRQL ,MECHANISM FOR :HYDRAULIC ARBARATUS Victor V. Blasutta, Columbus, and Wendell E; Reni'ck, Grove City, hio, assignors to The Denison Engineering Company,

Columbus,

Ohio, acorporaztionof Ohio.

A p cation. Apni1 .1.5, 1942, S rial No.i2 B

. l fThis-inventionrelates. generally ;to hydraulic apparatus and is particularly directed to .control valve-mechanism and hydraulic circuits for-hydraulic motorsparticularly of the reciprocating piston. type.

One of the objects of the invention is "to provide' a control "valve mechanism'which-"ma-y be employed in a hydraulic circuit to govern the operation of. a hydraulic motor whereby the movable element Qfthe motor, such as ,a piston of a. piston and cylinder type motor, may be caused to move rapidly during a portion ofthe working stroke of the motor and-thereafter develop a predetermined tonnage, the movable member operating at a slower rate during the exertion of the predetermined force.

Another object of the invention resides in providing a control valve mechanismrfor a hydrauiic press whichiva-lvemechanism will-permit the-connection ofboth ends ofthe power 'cylinderwith the sour-coefsupply-oiiluid pressure during-a *portion oft-he powe-rstroke-oi the-press ram andthen- 'automaticallyinterrupt'communication between-oneend of thepower cylinder-and the source of-fluid pressure tocause the ram to develop a desired force during the remainder oi-'-the stroke.

'further object of the invention isto a control valve of the types shown in the copending applicationof- 'Cecil Adams, Serial No. 589,163, filed April "-1-9, 15345, new Patent 249L355; dated December 1%, i949, to secure rapid movement of a press ram during its approach-toward-the 'workin 1a-press operation and automaticallychange-over to-slow speed andi-ncreased-"force after the work has been engaged by the "ram.

'A further object of the-invention is' to "provide a control valve mechanism having a casing and a pair of-mova-ble elements, which elements are movable relative to the casing and toone another to'alternately' direct fluid from a source of pressure (to oppositeends of "a power cylinder to 'efiect the reciprocation of a; piston therein, certain ofthe-elements being-so constructed and cooperating with the othenlementsthat one end oi-' the power cylinder will be-connected with the fluid-pressure source during --a port-ion of the time the other end of thejfpower cylinder is connected theretogthe decrease -in fluid-pressure in thefirst :mentionedend dueto -the--engagement-of-theram with the work and the consequent reductionin the rate oitravelthereoi; causing an adjustment oi'the'valve parts to connect thesaid one end-of 2 the power "cylinder to exhaust wherebythe full 7 Claims. (01;. rns-es);

2 supply of fluid pressurefrom the sourcewill-be directed'to the otherend of the-power cylinder to cause theexertion of the maximum iorc'e by the ram.

A still "further object of the invention :is to provide a four-way-valve havinge casing with a chamber, a sleeve-valve disposed for-reciprocation in the chamber, the sleeve valve having ports registering with recesses in the-valvebody, aspool valvemounted for-movement inthe sleeve valve to control communication between sets of ports the latter and a valve stemcarriedby the ca-sing and cooperating: with a paasagein the spool valve to interrupt communication-between certain ports inthe-sleeve valve and easing, the spool valve being normally urged toward -"one position and-'responsive'to fluid pressureto move opposition to the urgingmeans to another position, a decrease in -the fluid-pressure permitting the-spoolvalve to move toa third position wherein the passage in the spool .valve will-not be affected by-the-valve stem carried by thevalve casing.

A still" further object of the invention is to providea va1ve-oithe typeset iorthin the preceding-paragraph wherein the valve-stem carried by the'casing is eliminated and .a reduced diameter orifice substituted therefor, =the--val ve mechanism operating in substantiallythesame manner.

Another object of the invention isto provide -=a control-valve -mechan-ism having a casing-with -a bore-'forzthe reception-oi a sleeve val'vethe "casing having a plurality of recesses spaced longitudinally of the bore, the sleevevalverhavhig -longitudinally=spaced sets-oi ports forregistra tion with the recesses in the casing, the sleeve valve- 1 eceiving a spool valve whichis normally urged toward one position :to connect: certain 0f the por-ts in the sieeve vallve and -responsive--=to pressure to move opposition to-the urging means to another position to :oonnectother ports the sleevevalve, the :spool valvein-turnreoe'iving a slid-a'zble valve element which isailso 'nrged to a position to interrupt communication between certain ports in the firstuspool valve,

the slidable waive element :a'iiso beingresponsive to-fiuid pressure te-move to a position to-establish '-communication between ports in the spool valve, a reduction in the fluid pressure-=-permitting the last mentioned valve elemen t to return-to the position in which communication between the'ports i-n-the spool valve isinte rrupted. V

Further objects and advantages of the-present invention will be apparent from the ioliowing nected by a line 48 with the reservoir 2|. bore 34 is formed for the reception of a sleeve 3 description, reference being had to the accompanying drawings wherein a preferred form of embodiment of the invention is clearly shown.

In the drawings Fig. 1 is a diagrammatic view of a control valve formed in accordance with the invention with parts shownin section to illustrate the control valve mechanism and the power cylinder, the operation of which is governed by the control valve mechanism, the parts of the valve being shown in the positions occupied during the retraction of the ram of the power cylinder.

Figs. l-A, 1-3 and 1-0 are similar views showing the control valve mechanism in difierent stages of operation, Fig. 1-'A showing the valve parts positioned to initiate an operation of the ram; Fig. 1-3 shows the parts in position to cause a rapid advance of the ram; Fig. lC shows the valve parts in the positions occupied when the ram is exerting its maximum force while advancing. V V

Fig. 2 is a detail verticalsectional view taken through the control valve mechanism on the plane indicated by line II-II of Fig. 1.

V Fig. 3 is a similar view taken through a modifled'form of the control valve mechanism,and

Fig. 4 is also a similar view taken through a still further modified form of the control valve mechanism.

' Referring more particularly to the drawings, the numeral designates the completed hydraulic circuit. This circuit includes a source of fluid pressure having a reservoir 2|, a motor driven pump 22 and a relief valve 23, the latter being of any suitable type for limiting the maximum pressure to be generated in the hydraulic system. An exhaust line 24 leads from the relief valve 23 to the reservoir 2| to carry fluid by: passed by the relief valve when the pressure in the system reaches a predetermined maximum value. I

3 Line 25 extends from the relief valve, to the valve mechanism 26 forming the subject matter of the present invention. A pair of lines 21 and 28 lead from the control valve mechanism 26 to the upper and lower ends of a power cylinder 30. This power cylinder has a piston 3| disposed therein for reciprocation, aram 32 projecting from the piston through the lower end of the power cylinder. a

The valve mechanism 26 includes a casing 33 in which a longitudinally extending bore 34 is formed, the casing having annular grooves 35 to 4|, inclusive, formed therein and spaced longitudinally of the bore 34. The casing has a second bore 43 disposed in parallel relationship to the first bore, the casing having annular recesses 44 to 41, inclusive, formed therein and spacedlongitudinally of the second bore. Recesses 38 and 45 are connected at adjoining portions as are recesses'40 and 46, and, 4| and 41. As illustrated in Fig. l, recess 39 is directly connected with the source of fluid pressure by the line 25, while lines 2! and 28 directly connect the upper and lower ends of the power cylinder with thetop and bottom cylinder ports or recesses 40 and 31, respectively. Recess 41 is convalve 50, in which longitudinally spaced sets of laterally directed ports 5| to 58, inclusive, are formed, certain of these sets of ports being disposed in registration with certain of the grooves or recesses in the casing.

Y The sleeve valve 50 is closed at its upper end The by a cap 59, which is secured to the sleeve valve by machine screws 60. The sleeve valve in the first form of the invention illustrated, receives a shuttle valve spool 6|, which has upper and lower land portions 62 and 63 defining a groove 64, which establishes communication between certain ports in the sleeve valve in different positions of movement of the spool 6| therein. Normally the valve spool 6| occupies the position shown in Fig. 1, which is at the lower end of the chamber in the sleeve valve 50, being yieldably urged towards this position by a coil spring 65 disposed in a socket 66 formed in the upper end of the valve spool and a mating socket formed internally of the cap 59. When the spool valve occupies the position shown, the groove establishes communication between ports 56 which are then in communication with the fluid pressure source and ports 54, which register with the groove 31, the latter being connected as above-mentioned with the lower end of the power cylinder by line '28. I At this time fluid pressure from the source may flow to the lower end of the power cylinder to urge the piston 31 in an upward direction Fluid discharged from the upper end of the power cylinder during the upward movement of the piston will flow through line 21 to recess 40 from which it will flow through ports 51 to the interior of the sleeve valve at the upper end thereof. This fluid will flow outwardly through ports 58 to recess 4| from which it will flow by way of recess 41 and line 48 to reservoir 2|.

When the piston approaches the upper end of the power cylinder, an arm 61 secured to ram 32 will engage a collar 68 fixed on a shipper rod 10 which depends from the lower end of the sleeve valve 50. When the collar 68 is engaged by the arm, it will move the shipper rod and the sleeve .valve'50 in an upward direction in opposition to spring H, which is disposed between a, washer 12 in recess 35 and a collar 13 surrounding shipper rod 10 in the lower end of the recess 35. The ram will continue to move in an upward direction until, as shown in Fig. l-A, ports 54 are moved out of registration with recess 31. At this time fluid flow to the lower end of the power cylinder will be discontinued and the ram will stop moving.

When the sleeve valve is moved upwardly. as mentioned above, until communication between ports 54 and groove 31 is interrupted, communication will be established between ports 55 and recess 38 also as shown in Fig. l-A. At this time .valve 15 will be in the position shown in Fig. 1

and fluid admitted to the interior of the sleeve valve through the ports 56 will flow outwardly through ports 55 to recess 38, from which it will flow to recess 45. This fluid will flow upwardly in bore 43, refer to Fig. l, to recess 46 from which .it will flow through connecting recess 40, ports of the ram 32, a control handle 14 is operated to move a spool 15 disposed for adjustment in bore 43 to a position, seeFig. l-A, to interrupt communication between grooves 45 and 4B and establish communication between grooves 45 and 44. This operation is made possible by providing spool 15 with spaced land portions .16 and 11 which define a groove 18 in the exterior or the spool '15. (when grooves M ahd are in communication- "fiuid "flowing "from the power source throug h line-2S, re'cess fl, port's 51i and :55 torecessQQl Will -be directed through grooves 45, and 4'4to-ahole '81L'whioh connects groove 44 withgroove 36. lhe'lluid thus introduced to groovetfwill ilow through ports 51 to the interior I of the sleeve valve fl heneath shuttle valve 81. r

The pressureot thisifiu-id' :will movethe-shuttle valve I 6 l' upwardly in :opposition to the spring 1% toa positiohgsee Figs. lent l-#13 andhc, wherein the groove *fid in the-Shuttle valve will establ'ish communication between ports 2 56- and 51. The

source of fiuidrpre's'su're will then he' 'directl-y con- 1 neoted'with the upper ehdoi the power cylin'der and 'flu idfrom theipump will now into the bylin de'r above piston 31. 'ii his flui d wilhcausejithe piston to move in a downward uirection, exhaust? ing Lfluiii :from the lower end of the power :cylinder through line :28 to .lglroove J31. At this time ports 53, see Fig. ll- A, in'isleeve valve vtill will he in 're'gistrationwith the groove dlvand' fiuid will how to the interior-of the sleeve valve 510 through these ports and to an annularEgrooveBl formed in land :63 of: shuttle valve :spool 61.

Groove '81 is connected with the interior of the shuttle valve spool by ports 82 and the fluid will flowthrough theseiports to aspacasurrounding a reduced projection .83 formed i one plug 84, which is pinned in the center'bore of theshuttle valve spool. Immediately above the vpro-- jection '83, the center bore or the shuttle valve spool receives for sliding movement, a valve element 85 which has *a headedll'ower end 86 and a reduced extension 81 projected upwa'rdly therefrom this reduced extension being 'slidably received in 1a bushing 88 which is pressed into the centerbore of the spool :61. IA coil spring-"90 surrounds the reduoed portion "81,

theends of'this -'spring engaging the 'bushing 8 and the he'ad-llfi. Normallvthisspring-maintains theelementaa' inits lowennost position, a's il'lustrated in Figs. l and -l 'A,'v'/:herein-the1head '86 engages the projection 83. When, however mu'i'd is discharged from the lower end "of the power cylinder and this llui'd ils introdil'ced into th'c interior of the shuttle valve through ports 82, 'a pressure will be generated "which will :move the element against the opposition l of the spring 90 until communication is establishedbtween the space surroundingex tension 8 3 and the central bores formed in the 'ipl'ug 'fll, the valve element 85 and the spool BI. -Since during the initial portion or the stroked'f the ra m lflonly a minimum of opposition to movement is eneountered; the ram and piston will move ra i'dly discharging a rather large volume of fluid throughline 28. 'The flowo'fth is' large volume to exhaust is 'resis'tedby'the reduced passagesand openings formed inthe valve element 85' and cap with the fluid supplied fromthe pressure "source and will how 'tothe upper "end (if-the power cylinder. The "back pressure is transmitted through the center openin in pliig 84 to the fluid in the sleeve beneath the shuttle valve spool, this pressure operating to retain f-the shuttle valve in its elevated position wherein the source of fluid pressure connected with -;the upper end of the (power cylinder. The shuttle valve spool willlbe held :elevated by fthe -vbuck pressureeven thoughthe "valve spool" :1 511s re? turned to the normal position, see fligi l -Bgshy its springs I92 :and 93, 1thus :'discontinuingithe flow of fluid pressure from the --source fito the space beneath the shuttle valve. r it When the back pressure on the finidrexhausted through line 28: moves valv'ewelement 8511x1 2, position establishing communication @between ports 91 and 82, the fluid being jrexh austed through line I28 will "combine with the fluid from the pressure source, has mentioned above, and flow to the upper end of the power cylinder. The'eifectivearea of the apistonr3r'l *will'thus-rhe reduced to the area :0f. the ram 3'2, theiull' pump volume being efiective "over this reduced :area to cause 'movement of the .ram. linitial movement of the piston will cause the arm 'GTto move from the collar 68.,sperrnitting-spring1l *tosmove the shipper rod 10 andsleeve valve :50 down ward, until the end of thessleeve-valve engages thewasher l2, 'as sh'own in 1.-B amlr-L-G.

At this time ports '54 will register with groove 31 and fluid discharged from theipowervcylinder will then flow through ports-54. ThemapidamoVement of the piston 3| will continuenunti luthe ram meets an obstruction "which will offer suffioient resistance to the force exerted by thc'fram with the :reduced effective area to reduce theivspecd of ram motion. This reduction in rate-,of; mo 'tion of the ram will reduce the,"volumeof being exhausted through line -28 ,'whi'chtin turn will reduce the .pressure'in the bore inithe shuttle valve beneath the valve element and in the sleeve, valve beneath the-shuttle spool 51.- spring will thus :be permitted tomove valve-element '85 toward a position, see Fig. 1-r-Cv, to interrupt communication between gportsr8-2 and =9 l and' the shuttle valve spool will "be-moved by "Spring-p65 to a position wherein the upper end-of the shuttle valve wi'llbefspaced from cap 59. Mter the element 85 has moved the -distance "necessary 1 to interrupt communication between "ports :82 and :9! I the full xpump volume willb'e available over the entire upper :surface of the pistonpil'-1%ende11- ving this :surface effective :to cause movement; of the ram. With the increasedeffiective areacof th'euramfiavgreater force will be exerted which will "cause the ram movement-to continuerimti-l the ram "meets an obstruction which wil-lmfi-er :sulficient resistance tomovement of the sgpiston at as to cause'therelie'f valve '23 to vent the'entire pump volume to the tank or-reservoirzllt. At this time the ramwill :be exerting the; tonnage ;for which the relief valve-had lpreviously-rbeen ad'Justed. 1 v

Whenthe relief valve spills' fiui'd"'to reservoir 2 I, ram 32 will cease to moverand :texhaust flow of fluid through :line 28, will :also :cease. The lipid 'beneath'the shuttle valve, will be'dissipated through the center cpeningsfinitherplng fla valve element 85 and shuttle valve' fi'l, "permitting spring :65 to move the shuttle valv'e back-to its lowermost position, :as shown :inrFig. 1, wherein groove '64 establishes communication'hetweenithe source of fluid pressure andthe :l'ine leadingizo the lower end of the p'ower cylinder. At time, the ram "will move i'n'anrupwardvdireotion, discharging 'fluid "from the upper endof the power cylinder, through line 11 .a'as'ipreviously described. The final stage of the "return :move ment of the ram will cause the upward movement of the shipper rod 'lu'andsleeve valve omalso as previously described, until fluid flow -to line 28 is discontinued, the fluid from lthe pre ss'imc source then being directed through ports 55'to grooves 38 and 45 ,from which the fluid will be exhausted to the reservoir as outlined'previously.

- Ii continuous operation of the ram is desired the valve spool I5, may be retained in a position to establish communication between grooves 44 and 45, so that when fluid is supplied to groove 45 after the upward movement of sleeve valve 50 a subsequent ram .operation will be initiated automatically.

In .the form of the invention illustrated in Fig. 3', the valve mechanism is substantially the same as that shown in Figures 1 and 2, except the shuttle valve spool I does not contain the valve element 85, nor, the plug 84, neither, is the shuttle valve I00 provided with the ports SI.

In the form of invention shown in Fig. 3, the valve body 35A is provided with a passage IOI, which extends from the bottom cylinder port 102, to the groove 39A which communicates with the line 25 leading from the fluid pressure source. Passage IOI contains a spring pressed check valve I03 which comprises a valve seat I04, a ball valve I and a spring I06, the check valve I03 serving to prevent fluid flow from the groove 39A to the bottom cylinder port I02, but permitting flow in the opposite direction.

Fig. .3 illustrates the parts of valve mechanism in the positions which they will occupy during the portion of the pressing stroke of the ram immediately following the initial movement of the ram, that is, after the ram has moved a distance sufficient to permit the spring II to move sleeve valve 50 downward until the lower end has engaged the washer 72. As the ram moves in a downward direction fluid will be discharged from the power cylinder to the bottom cylinder port I02, a portion of this fluid flowing through passage I01 to groove 31. Some of this fluid will be permitted to flow through ports 54 to a transverse passage I08 formed in the shuttle valve and outwardly therefrom through a'longitudinal passage IIO provided in the shuttle valve. The flow of this fluid will be resisted by an orifice I I I, formed in a plug I I2, which is threaded into an opening provided in the cap 59A for the sleeve valve 50. Due tothe resistance to flow offered by the orifice I I I, a back pressure will be created on the exhaust fluid which back pressure will be transmitted through an opening in the lower end of the shuttle valve to the space in the sleeve valve .50, beneath this shuttle valve. The reaction of this fluid pressure will tend to retain the shuttle valve in its elevated position wherein the upper end of the shuttle valve is disposed in sealing engagement with the underside of the cap 59A. The back pressure on the exhaust fluid will also be applied to the ball valve I05 moving the same in opposition to the spring I06 to an open position wherein the exhaust fluid will combine with the fluid supplied from the pressure source and will flow through passage H3 to the top cylinder port II 4 from which it will flow through line 21 to the upper end of the power cylinder. Passage II3 contains an orifice element II5, which insures a sufficient pressure on the operating fluid as to make the valve mechanism operate satisfactorily. The mechanism shown in the modified form has the same effect on the operation of the ram as the mechanism shown in the first form of the invention" described, that is, when exhaust fluid flows through passage IM and combines with the fluid pressure supply the effective area of the piston in the power cylinder will be reduced to the area of the ram, the entire pump volume being"- ex erted on the reduced area to, cause a rapid movement of the ram. Due to the reduction in the effectivearea the resultant force of the ram will be reduced and consequently when'the ram engages an obstruction I which ofiers sufiicient resistance, the rate of movement of the ram=will decline. Because of, this reduction in the rate of movement, the back pressure on the exhaust fluid will ,be reduced permitting the shuttle valve spring to start to move the shuttle valve toward a lower position. ,When this movement occurs the upper end of the shuttle valve will move away from the under surfaceof the cap 59A, permitting the exhaust fluid to by-pass the orifice III, which will furtherreduce the back pressure. After the back pressure falls sufliciently spring I06 willreturn ball valve I05 toits seat causing the exhaust fluid to cease flowing through passage IOI,'whereby,the eflfective area of the piston will be increased to the full diameter thereof. The full pump volume will then be exertedover the full area of the piston; causing the force exerted by the ram to increase, which will permit the ram to continue to move, although at a reduced rate. The flow of exhaust fluid will be sufli'cient to maintain the back pressure necessary to hold the shuttle valve in a partially elevated position to continue the communication between the fluid pressure source and the line leading to the upper end of the power cylinder. The shuttle valve will be held in this position until the resistance to movement of the ram reaches a magnitude suflicient to :cause the relief valve to spill the pump volume to the reservoir ZI, at which time the ram will stop, permitting the exhaust flow to cease also. The cessation of exhaust flow will cause the dissipation of the back pressure and permit the shuttle valve to move to its lower position wherein the source of fluid pressure will beconnected with thelower end of the power cylinder. The ram will then be moved in its return stroke preparatory to starting a subsequent cycle, of operation.

In the form of the invention illustrated in Fig. 4, the mechanism is substantially the same as that illustrated in Fig.3, except that the passage .l0I, has been omitted and an exterior fluid conducting line II6, substituted therefor. This line contains a check valve III corresponding in fimction to the check valve I03. The same shuttle valve I00 is employed but the plug II2 with the orifice III has been eliminated, the function of these elements being performed by a valve stem II8, \vhichis adjustably carried by the cap II9 for the casing I20 of the valve mechanism. Valve stem I I8 projects downwardly through an opening I2I formed in cap-59B for spool 50, the

lower end of the valve stem registering Wlthlh central longitudinal passage IIO of shuttle valve spool I00.

When this shuttle valve spool is elevated through the introduction of fluid pressure to the space beneath the same, the valve stem will restrict the fluid flow through the passage IIO causing a back pressure to be generated on the be conducted to, the upper end of the power'cylinr der; The operation of the power cylinder will be substantially the same as with the other valve mechanisms above described, the combination of the exhaust fluid with the fluid from the pres sure source serving to reduce the effective area of the piston. in the power cylinder thus making the full pump. volume available over a piston area equal to the ram area. When the rate of ram movement declines due, to the fact that the ram is exerting a force insuflicient to cause movement, the. back pressure will fall, permitting the shuttle valve tolower a distance sufficient'to allow the fluid flowing from the power cylinder to be discharge to the reservoir, rather than be combined with the pressure source.

. The retraction of the ram when the; modified valve mechanismv shown in Fig. 4 is employed is the same as when the other forms of valve-mechanisms are employed. It: will be apparent from the foregoing description, that means have been provided for controlling the flow. of fluid from. a source of pressure to a. fluid motor which will permit the efiective area of the piston of the motor to be reduced whereby the full, volume of the pressure source is available to cause a rapid movement .of the piston.

A number of modifications of the valve mechanism have been shown. The. operation of the fluid motor controlled by the various modifications is identical, the rapid rate of exhaust fluid flow from the power cylinder serving to create a! back pressure, which is utilized to establish communication between the exhaust line and the inlet line, or, fluid pressure source and a diminution ofsufiicient back pressure, due to a reduction in the rate of movement of the piston of the motor, being'employed to increase the effective areaof the piston so that the full volume of the pressure source will be applied to the increased piston area to increase the force exerted. While the mechanism is diflferent in each of the modifications the fundamental principles of operation are identical.

The claims which follow have been drawn with the object of covering all of the forms shown and any other modifications embraced thereby;

We claim:

l In a hydraulicsystem, a motor of the cylinder and piston type; a source of fluid pressure;- control valve mechanism between said source and said motor comprising a casinghaving a chamber and inlet, cylinder and exhaust ports; means establishing communication between said inlet port and said pressure source and between the ends of said cylinder and said cylinder ports; relatively movable valve elements in, said chamber for alternately connecting the inlet and exhaust ports with said cylinder ports to cause the reciprocation of said piston in said cylinder; a passage providing for fluid flow from a selected cylinder port to said inlet port; a normally closed-valve in said passage; a fluid flow resisting: element cooperating with a selected movable valve element, when, it is inuacertain position, tolimit the fluid; flow from. said. selected cylinder port to exhaust to create a back pressure, said selected valve siement'being retained in said certain position and said normallyclosedvalve being opened by such back pressure; and .meanslfor moving said "selected salve element to a position to render said flow-resisting element ineffective upon diminution of said back pressure.

2. Control valve mechanism for a reversible fluid motor comprising a casing having a chamber and inlet, forward-and-reverse-motor,.and exhaust ports communicating with said chain-- ber; a primary valve element disposed for movement in said chamber, said primary valve element being-tubular and having ports registering with the ports in said casing in various positions of said element in said chamber; a secondary valve element disposed for movement in, said primary valve element to alternately connect said inlet and exhaust ports with said forward and reverse motor ports; resilient means normally urging said secondary valve element toward a position in which said reverse motor port is connected with said inlet and said forward motor port is connected with said exhaust; means for momentarily applying fluid at inlet port pressure to said secondary valve element to move the same in opposition to said resilient means to a position in which said forward motor port is connected with said inlet and the reverse motor port is connected with said exhaust; flow-restricting means between said reverse motor port and exhaust to create back pressure, said, back pressure being applied to .said sec.- ondary valve to retain the same against movement by said resilient means; a second flow-resisting means operative when said secondary valve element is held against movement by :said resilient means to further increase the back pressure; a valve controlled passage extending between said reverse motor and inlet ports, the valve in said passage being responsive to .the increased back pressure to permit flow from said reverse motor port to said inlet port.

3. Control valve mechanism for a reversible fluid motor comprising a casing having a chamber and inlet, forward-and'-reverse-motor, and exhaust ports communicating with said chamber; relatively movable valve elements disposed in said chamber, said valve elements being operable in a first relative position of movementto connect the inlet'and forward-motor ports and the reverse motor and exhaust ports, and-to reverse such connections in -a second relativeposition of movement; fluid flow controllingmeans for momentarily applying fluid at inlet port pressure to said valve elements to dispose them in the first relative position; fluid flow-resisting means operative when said valve elements are in said first relative position to limit fluid flow from said reverse-motor port to exhaust to create a back pressure; a valved passage extendinggbetween said reverse-motor port and said-inlet, the valve in said passage being responsiveto back pressure to permit fluid flow only in the direction from said reverse-motor portto said inlet; resilient means normally urging said valve .elements toward said second relative position, initial movement of said valve elements from said first'toward said second relative position rendering said flow-resisting means-inoperative; and a second flow-resisting meansoperative. to limit fluidflow from said reverse-motor port to exhaust when the first-mentioned flow-resisting means. is inoperative to create a lesser back pressure, said back pressures being applied to said valve elements. to oppose movement thereof byv said resilient means. v

4. Control valve mechanism for a reversible fluid motorcomprising a casing having a, chamber and inlet, forward-and-reverseemotori and exhaust ports communicatingwith said chamber; relatively movable valve elements disposed in said chamber, said valve elements being operable in a first relative position of movement to connect the inlet and forward-motor ports and the reverse motor and exhaust ports, and to reverse such connections in a second relative position of movement; anexhaust passage provided in one of said elements, said passage connecting said reverse motor port with saidexhaust port in the first position of movement of said elements; a flow-resisting valve member at least partially obstructing said exhaust passage when said elements are in said first position of movement to limit such flow and create a back pressure; a valved passage extending between said reverse motor and said inlet port, the valve in said passage being responsive to such back pressure to permit fluid flow only in the direction from said reverse motor port to said inlet port; resilient means normally urging said valve elements toward said second relative position, initial movement of said valve elements from said first toward said second relative position serving to relieve the obstruction caused by said flow-resisting valve member to increase the exhaust flow through said exhaust passage and decrease the back pressure whereby floW from said reverse motor port through said valved passage to said inlet port will be discontinued.

5. Control valve mechanism for a reversible fluid motor comprising a casing having a chamber and inlet, forward-and-reverse-motor, and exhaust ports communicating with said chamber; valve elements in said chamber, said elements being movable relative to one another and said casing to alternately connect said inlet and exhaust ports with said forward and reverse motor ports to cause forward and reverse operation of said motor, one of said valve elements being responsive to fluid pressure to establish communication between said inlet and forward motor ports and between said outlet and reverse motor ports; a passage extending between said reverse motor port and said inlet port; flow resisting means between said reverse motor port and said exhaust port, said resisting means causing a back pressure; and yieldably closed valve means in said passage to prevent fluid flow from said inlet to said reverse motor port, said back pressure serving to retain said pressure responsive valve element in position to connect said inlet and forward motor port and to open said yieldably' closed valve to establish communication between said reverse motor and inlet ports while the latter is connected with said forward motor port.

, 6. Control valve mechanism for a reversible fluid motor comprising a casing having a chamher and inlet, forward and reverse motor and exhaust ports; primary valve elements disposed in said chamber for movement relative to one another and said casing alternately connect said inlet and exhaust ports with said motor ports to cause forward and reverse operation of said motor, one of said primary valve elements being responsive to fluid pressure to establish communication between said inlet and forward motor port and between said exhaust and reverse motor 'ports; a passage extending between said reverse 'motor port and said inlet port; asec'ondary valve element in said passage;'spring means yieldably urging said secondary valve element toward a passage closing position; flow resisting means between said reverse motor andexhaust ports, said resisting means causing a back pressure, said fluid pressure responsive primary valve element and said secondary valve element being exposed to the back pressure to retain the former in pothe primary valve element to a position to inter-.

rupt fluid flow between said inlet and the forward motor port.

7. Control valve mechanism for a reversible fluid motor comprising a casing having a chamber and inlet, forward and reverse motor and exhaust ports; a ported sleeve valve disposed for movement in said chamber; a ported shuttle valve disposed for movement in said sleeve valve to establish communication between certain sets of ports in said sleeve valve; a third valve element disposed for movement in said shuttle valve to control communication between the ports in said shuttle valve; spring means tending to yieldably retain said valves in predetermined positions wherein said inlet port is connected with said reverse motor port and said exhaust port is connected with said forward motor port; means for momentarily directing fluid pressure against said shuttle valve to move the same to a second position to connect the inlet port with said forward motor port and said reverse motor port with said exhaust port; and flow resisting means between said reverse motor and exhaust ports and operative when said shuttle valve is in said second position to resist fluid flow from said reverse motor port to exhaust to create a back pressure, such back pressure being applied to said shuttle valve to retain the same in said second position, said back pressure also being applied to said third valve to move the same to a position to establish communication between ports in said shuttle valve to connect said reverse motor port and said inlet while the latter is connected with said forward motor port, the spring for and the size of said third valve being so related to the spring for and size of said shuttle that a predetermined diminution of such back pressure will cause the closing of said third valve prior to the complete movement of said shuttle valve out of said lastmentioned position.

VICTOR V. BLASUTTA. WENDELL E. RENICK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 523,419 Thorpe July 24, 1894 1,931,452 Wheeler Oct. 17, 1933 2,142,628 Ballert Jan. 3, 1939 2,160,217 Kingsburg May 30, 1939 2,200,998 Schnuck May 14, 1940 2,283,124 Peterson May 12, 1942 2,316,471 Tucker Apr. 13, 1943 2,431,032 Ernst Nov. 18, 1947 2,443,642 Rockwell June 22, 1948 2,491,355 Ada-ms Dec. 13, 1949 

